What exactly is “chronobiology”?

The Science

Chronobiology is a science that studies how the clock inside the brain interacts with time cues in the environment. The daily alternation of light and darkness is the main cue that keeps our inner clock in synch with the outside world. When such cues are absent or weak, our circadian rhythms of body temperature, hormones, sleep and alertness — and yes, even mood — get out of adjustment with earth’s rotation about the sun.

The Technologies

Methods used in clinical chronobiology include timed exposure to bright artificial light to reduce insomnia or sleep-wake disturbances due to shift work, and the use of a spring-like lighting environment to fight winter depression. New applications include light therapy for chronic depression and depression during pregnancy. The underlying idea is that even when there is plenty of light outdoors, our urban lifestyle tends to keep us in the dark, relatively speaking, making us vulnerable to mood slumps.

Is it safe to use a light box if I am on intravenous antibiotic therapy with doxycycline for Lyme Disease? I have been instructed to avoid sunlight.

You can use light therapy, but you must use a system that completely shields ultraviolet (UV) light exposure. There is only one such 10,000 lux fluorescent system that clearly meets these standards (for info, see //www.cet.org/store/). In the future, other possibilities may include head-mounted units with light-emitting diodes (LEDs) to generate the signal without UV, however such units have not yet been demonstrated effective relative to placebo controls for antidepressant treatment. One final clinical note: some patients who have responded well to bright light therapy report that their mood worsens and the light becomes aversive while they are taking antibiotics for acute infections. Whether this might also apply to Lyme disease, which is more chronic, we simply do not know.

Can too much neon light be bad for you? I live under a huge neon sign that shines through my windows all night.

Your own sleep quality, daytime energy and mood state comprise the acid test of whether such nocturnal illumination is bad for you. In general, we would predict it would indeed be bad. We call this “nocturnal light pollution.” We believe it is important for bedrooms to be dark during the beginning and middle of the sleep period. Toward the end of the sleep period, however, exposure to gradually increasing dawn light — whether through the window or from an artificial dawn simulator (see //www.cet.org/store/) — can help stabilize sleep, make waking up easier, and enhance daytime mood and energy. Your neon sign will not do this job.

How can I tell if the diffusion filter on a particular commercial apparatus is adequate?

There are two issues here. First, you want the screen to project fairly even light, so you cannot see the bare outline of the fluorescent tubes behind it. Second, the screen should not transmit significant ultraviolet (UV) radiation. Almost no manufacturer offers credible evidence of UV filtering; rather, they just make the claim and count on the consumer to believe it.

Technical Details of UV Exposure

One reason for this unhappy situation is that ascertainment of UV exposure is a technical matter — it is expensive to produce the data, and most consumers would not know how to interpret the data. If you are scientifically smart, you can challenge a manufacturer to show you a complete graphical spectral-output curve, starting in the low-UV range (around 200 nanometers) and extending throughout the visible range (up to about 750 nanometers). If there are any prominent bumps in the curve below 400 nanometers, you should reject the device. Two screen compounds, OP-3 and polycarbonate, have been shown to filter UV maximally, so you could look for devices with such screens.

Somehow, I feel like it is always winter. I have never been able to wake up early in the morning even with the sun out. (Making classes in college was a disaster). I drag around for half the day, although I seem to recover by evening. I cannot control my weight with any diet. I try to make friends, but cannot keep them. I feel so isolated.

Depression is a complex beast, and it can come with all kinds of patterns. Yours does look winter-like, and we know that for some people this symptom picture can last year round. There is a hint in what you say that light therapy could be effective for you regardless of the season. Your late waking indicates that your circadian rhythms are mal-synchronized with local clock time. This could be due to a genetic predisposition, but it also could be due to excessive light exposure in late evening – when you tend to feel better – because evening light can force the biological clock later, with resulting late awakening. For starters, make sure your indoor evening light is kept at a low comfort level that does not energize you. Whether the basic problem is genetic or environmental, morning light therapy could provide a solution by shifting your circadian rhythms earlier, just as it does for winter depression. You can expect to be able to wake up earlier, and there is good hope for an antidepressant effect. Indeed, a recent clinical trial at Columbia University Medical Center and Wesleyan University found that about half of patients with chronic, non-seasonal depression responded to light therapy just as well as SAD patients respond in winter. Definitely worth a try!

If one is sensitive to some fluorescent light — for example, I get migraines — can light boxes be used to treat SAD?

Adverse reactions to fluorescent lighting is usually due to poorly designed lighting installations with a high glare factor, or electronic ballasting of low, 60-Hz frequency. Most likely, you would not experience such headaches using a well-designed light box with a smooth diffusion screen and high-frequency ballasting. Headache (though not migraines) is fairly frequently reported as a side effect during the first few days of light therapy, but the problem usually resolves quickly. If not, reducing light dose — for example, with shorter treatment sessions — often provides relief. Extremely few users have experienced long-term, intractable headache under light therapy.